Japanese Patent No. 4458359 (U.S. Pat. No. 7,322,729) has proposed, among other embodiments, a conventional lighting device utilizing an LED light source and a lens body.
As shown in FIGS. 1A to 1C, one embodiment disclosed in the conventional art patent document can be formed as lighting device 200 and can include a plate-like lens body 210 and an LED light source 220 disposed in front of the surface of the lens body 210. The lens body 210 can include a first side surface 211 with a width dimension longer than a thickness dimension and serving as an elongated rectangular light exiting surface, and a second side surface 211 opposite to the first side surface 211.
In the lighting device 200 with the above configuration, the action of the lens body 210 having optical elements with refracting or reflecting action can cause the first side surface 211 to radiate light in a linear shape, thereby constituting a line-shaped light source. However, since the optical axis AX1 of the lens body 210 and the optical axis AX2 of the LED light source 220 are orthogonal to each other in this embodiment (see FIG. 1B), it is difficult to design the lamp layout.
To cope with this problem, as shown in FIG. 2, the LED light source 220 can be disposed so as not to face the main surface of the lens body 210, but to face the side surface of the lens body 210, thereby achieving the line-shape light source for emitting light in a linear shape.
In this case, in order to increase the utilization efficiency of light radially emitted from the LED light source 220, the area of the light incident surface may be increased. However, the lens thickness H of the lens body 210 must be increased in this case, requiring a thick molding for the lens body 210. This may increase the weight of what should otherwise be a light-weight lighting device 210.